Method of treating slack wax



1943- R. F. PFENNIG trim. 2,315,077

- HETI'IOD OF TREATING SLACK WAX Filed Aug. 24, 1940 2 Sheets-Sheet 1Fan/vaca- 1 WAX con r0 arm/c Fez. on. I.

rewaxe'p 0/4 March 30, 1943.

R. F. PFENNIG ETAL METHOD OF 'I REATING SLACK WAX Fiied Aug. 24, 1940 2Sheets-Sheet? Patented Mar. 30, 1943 METHOD OF TREATING SLACK WAX ReubenF. Pfennig and Claude R. Davis, Baytown, Tex., assignors to Standard.Oil Development Company, a corporation of Delaware Application August24, 1940, Serial No. 354,066

10 Claims.

This invention relates to a refining operation and is particularlyconcerned with an improved process for the refining of petroleumhydrocarbons. In accordance with the present process petroleumhydrocarbons or fractions derived therefrom are treated with ananhydrous molten alkali under conditions to produce high yields ofproducts of improved quality. The present application contains subjectmatter in common with the subject matter of application 331,698, filedApril 26, 1940, for Pfennig and Davis, and is a continuation in part ofsaid application.

It is well known in the art to refine and process mineral oils andpetroleum hydrocarbons by various procedures in order to producesatisfactory refined products. In these operations it is usuallyessential that the refined product be neutral or non-acid, that it berelatively stable in that deterioration of the product will not occurover a relatively long period of time, and that its color, as well asits color stability, be satisfactory. Thus various processes aredirected specifically to the production of neutral, stable, and colorsatisfactory products in the refining of mineral oils such as in theprocessing of low boiling petroleum oils, motor fuels, kerosenes,cracked naphtha fractions, heating oil fractions, lubricating oils, waxfractions, as well as solvent extracts. For example, in the processingof lubricating oil stocks derived from naphthenic crudes, it is knownthat certain constituents such as naphthenic acids and the like mustbe-removed' for the production of neutral distillates. A conventionalprocedure for accomplishing this result is to inject aqueous solutionsof sodium hydroxide or equivalent solutions directly into the still,preheater, or fractionating tower and to allow the distillation toproceed in the presence of this alkali. Various modifications of thisprocess are also employed, one of which is to inject dry lime into thepreheater or still in order to neutralize acidic compounds, particularlynaturally occurring acidic oxygen-containing compounds, which results inan improvement in the color and quality of the refined oil. It is alsoknown to pass mixtures of petroleum vapors and steam through strongaqueous alkali solutions at elevated temperatures. Another practice isto contact petroleum vapors with fused caustic in a distillation towerby circulating the liquid caustic over several plates near the bottom ofthe tower. By operating in this manner, the vapors from the still arepassed countercurrently through the liquid caustic, thus neutralizingacidic materials and efiecting a color stabilityimprovement in thedistillate. Hydrocarbon oils have also been extracted with aqueoussolutions of sodium hydroxide at relatively high temperatures, forexample, in the range from about 300 F. to 400 F. and at elevatedpressures such as 300 pounds to 400 pounds per square inch. However,while accomplishing satisfactory results in general, these processespossess certain disadvantages which increase operating difficulties andrender the operations relatively expensive. A distillation operationconducted in the presence of a solution .of sodium hydroxide tends tocause deposition of the caustic on the walls of the equipment andheating means, which materially decreases heat transfer rates andincreases operating costs. Furthermore, it is necessary to frequentlyclean the equipment, thus substantially decreasing its yearlythroughput. Other disadvantages encountered in current processes are theextensive pressure drops which are incurred, particularly in vacuumdistillation operations, as well as in the formation of emulsions whichare difficult to break.

In order to produce light naphtha products having a satisfactorystability, color, and other desirable characteristics, it is theconventional practice to process these materials by variousmodifications of. acid treating, doctor sweetening and rerunningoperations. Heating oil distillates, as well as related oils boiling inthis boiling range are similarly refined utilizing modifications of acidtreatment, water washing, alkali washing, and distillation operationsdepending to some extent upon the character of the feed oil. Commercialand highly refined waxes having a satisfactory color and stability areproduced by various operations comprising acid treating, causticwashing; rerunning, percolation, through bone 7 char or other similaradsorbent, and related stages. Solventextracts produced-by the utiliza-"tion of solvents of the class which have a preferential selectivity forthe relatively more aromatic type constituents as compared to therelatively more parafilnic type constituents, as for example phenol,furfural, sulfur dioxide, cresol, nitro benzene, aniline, beta betadichlor-diethyl ether, and the like, are also further refined usingconventional acid treating and various distillation and rerunningstages.

We have now discovered an improved process for the production of highyields of improved quality products whichhave a better color and colorstability than has heretofore been secured by known processes.Furthermore, in the case of relatively low molecular weight distillatessuch as cracked naphthas, kerosenes, and heating oils, our processsubstantially completely removes the mercaptan sulphur compounds. Ourprocess comprises contacting mineral oils, particularly petroleumhydrocarbons, in the liquid state with an anhydrous fused alkali at atemperature above the fusing point of the alkali. A preferredmodification of our invention comprises contacting the feed material inan initial stage with an anhydrous fused alkali at a. temperature abovethe fusion point of the alkali and thenin a secondary stage distillingthe feed oil under controlled conditions. Our process produces finishedproducts which have a low neutralization value and which haveexceptionally good cast and high color stability. In accordance with ourprocess the feed material is contacted in the liquid phase atapproximately... I'

l is removed from the unit 3| by means of line atmospheric pressure withan anhydrous caustic the waxy constituents contact bone charcoal.

molten alkali which may or may notbeimi'xed with another anhydrousmaterial capable of lowering its fusion point, butwhich; does" changeits chemical activity. r

Our invention may be readily understoodby reference to the attacheddrawings illustrating modifications of the same. Figure 'lillustratesthe adaptation of our invention in the manufacture of high qualityrefined waxes, whileFigure 2 illustrates the adaptationfor theproduction of high quality products from feed oils employing a solventextraction stage. Referring specifically to Figure 1, a feed oil, whichforvthe purpose to remove by means of line 36 a bottoms product. Itis tobe understood that distillation tower 28 may comprise any number oftowers arranged in any desirable manner and that one or more sidestreams may be segregated. The overhead waxy constituents removed bymeans of line 29 are condensed in condenser 36 and passed to sweater 3|.A sweated waxy fraction .32 and passed through filtration unit 33 inwhich A refined high quality wax fraction is withdrawn from unit 33 bymeans of line 34 and handled in any manner desirable.

Referring specifically to Figure 2, a feed oil, which for the purposesof description is taken to be a petroleum oil, islintroduced intosolvent treating plant 56 by means of line 5|. In this plant. the oil,is contacted with a solvent of the class which has a preferentialselectivity for the I relatively more aromatic constituents as comofillustration is assumed to be a wax-containing'lubricating oil fraction,is introduced into dewaxing plant-l by means of feedline ;2. Wax plant Imay'comprise any suitablenumber of units and be operated in anyconventional manner for the removalandsegregation of a waxy constituentfraction and for the production of a satisfactory dewaxed oil; Thedewaxed oil is withdrawn from plant I by means of line 3, while the waxyconstituents are removed by means of line 4 and introducedinto storagetank 5. The waxy stock is withdrawn from storage tank 5 and introducedinto furnace 6 for heating by means of line land pump, 8. By means ofline 9, the heated oil is withdrawn from furnace 6 and mixed with afused alkali, introduced by means of line Ill, and the resultant mixturepassed into mixer ll. Forpurposes of description the fused alkali istaken'vto be an anhydrous mixture of sodium hydroxide and sodiumcarbonate. The mixture comprising waxy constituents, fused sodium.hydroxide, and sodium carbonate is withdrawn from mixer l l by means ofline l2 and introduced. into settling zone I3. Settling zone 13 issodesigned that the waxy constituents arein contactwith a fused alkaliforan optimum time period at thedesired temperatures. The :desiredtemperature in settling zone '13 is maintained by heatingmeanslicomprising lines. I5and I6. The fused alkalimixture is withdrawnfrom settlingdrum l3 by means ofline .l1 and recycled to the mixer asdescribed by means of recycle pump I 8. Spent fused alkali may bewithdrawn from the system by means of line I9, while fresh or make-upa1- kali may be introduced from make-up alkali drum 26 by means of pumpZIand line 22 The desiredtemperature is maintained in make-up drum 2 0by means of heating coil 23 which comprises lines 24 and 25.Thealkali-contacted waxy constituents arewithdrawn from settling zone I3 by means of line 26, passed through furnace 21, and introduced intodistillationtower 28. Under certain conditions it maybe desirable toremove the waxy constituents from pared to the relatively moreparafiinic constituents. For purposes of description it is assumed thatthe solvent comprises phenol, which is in- .troduced by means of line52. Temperature and finic phase which iswithdrawn from the system thesystem by means of line 35. These removed constituents may be handled inany manner desirable and further refined by sweating and filtration.However, in general it" is preferred to distill the waxy, constituentsas described.

Temperature and pressure conditions of distilla-1 tion tower 2c areadapted v to remove overhead .by means of line 29 the desired products,and

by means of line 53, and a highly aromatic sol- .vent extract phasewhichis withdrawn by means of line 54. It is to be understood thatsolvent treating plant 50 may comprise any suitable number of stages ormay comprise conventional solvent countercurrent treating towers. Theoperation may be conducted and operated in accordance with conventionalmethods. The solvent extract removed by means of line 54 is introducedinto solvent recovery unit 55 in which the solvent is removed by meansof line 56 and preferably recycled while a solvent free; extract oil isremoved by means of line 51 and passed to storage tank 58. Thesolvent-free extract is withdrawn from storage tank 58 and introducedinto furnace line'62; and then mixed with an anhydrous fused alkalLwhichis introduced by means of line 63. .The resultant mixture isthen-introduced into jmixer 64. For purposesof description the fusedalkali is taken to-be an anhydrous mixture of sodium hydroxide andsodium carbonate. The mixture comprising the solvent extract, the fusedsodium hydroxideand sodium carbonate is withdrawnfrom mixer-64. by-meansof line 65 and introduced into settling zone 66. Settling zone 66 isdesigned so that thesolvent extract is in con tact with the fused alkalifor the desired time period at the optimum temperature. The desiredtemperature in settling zone 66 is maintained by heating-meansSLThefused alkali mixture is withdrawn from settling. zone 66 by means ofline 66 and,-by means of. pump 69, it is recycled to line 62 where it ismixed with the oil'withdrawn from furnace 59. Spent. fused alkali may bewithdrawn from the system by means of line 16, while fresh or make-upalkali may beintroduced from make-up alkali drum 1 l by means of pump 12and .line 13. The desired temperature is maintained 1n makeeup drum "Hby means of heating coil arrangement 14. The alkali-contacted solventextract 1s withdrawn from settling zone 66 by means of line .15, andmay-be withdrawn from the system by means of line 16 andfurther refined in-.any,-des1rable manner. 'However, it is preferred toipass thealkali-contacted solvent extract oil through furnace T! and then todistillation tower 78. Temperature and pressure conditions ofdistillation tower 18 are adapted to remove overhead by means of line 79the desired products and to remove by means of line 80 a bottomsproduct. Distillation tower 18 may comprise any number and arrangementof fractionating or distillation means.

The process of the present invention may be widely varied. The inventionessentially com prises contactin feed materials in the liquid state withan anhydrous fused alkali at a temperature above the fusion. temperatureof the alkali. In accordance with the preferred modification of theinvention, the alkali-contacted feed material is then distilled innsecondary stage. The process may be adapted to the treatment of any feedoil. The invention, however, is particularly suited for the processingof petroleum hydrocarbons such as light naphthas, kerosene fractions,cracked naphthas, and heating oil fractions. The invention is especiallysuitable for the production of high quality refined waxes and for theproduction of high quality refined products derived from solventextracts, particularly phenol extracts.

Although any anhydrous fused alkali may under certain conditions beemployed, we prefer'to utilize anhydrous alkali metal hydroxides, suchas sodium hydroxide and potassium hydroxide. 7

An especially desirable treating agent comprises a mixture of sodiumhydroxide and potassium hydroxide, particularly when the concentrationof the sodium hydroxide is in the range from about 25% to 85%. Ingeneral, the most satisfactory operation is secured when the sodiumhydroxide, potassium hydroxide mixture comprises from 45% to 55% ofsodium hydroxide. Other desirable alkali mixtures comprise sodiumhydroxide admixed with various anhydrous inorganic salts which arecapable of lowering the fusion point of'the sodium hydroxide.Particularly desirable salts are sodium carbonate, sodium sulfide,sodium bromide, sodium iodide and sodium sulfate. An especiallydesirable alkali mixture utilizing sodium hydroxide comprises a mixtureof sodium hydroxide and anhydrous sodium carbonate. When employing thismixture, it is desirable to use at least 75% sodium hydroxide,preferably from 85% to 95% sodium hydroxide. A particularly desirablemixture comprises 92% sodium hydroxide and 8% sodium carbonate. Thealkali should be substantially anhydrous and in no instance is itdesirable that the moisture content of the treating alkali or alkalimixture exceed about 2.0%. In general, the moisture content of thealkali treating agent should be below about 0.5% and should preferablybe anhydrous.

The time of contact between the fused anhydrous alkali mixture and theoil will depend primarily upon the intimacy of contact attained betweenthe oil and alkali mixture and to some extent upon the temperature atwhich the oil is treated. However, when treating a feed oil derived froma naphthenic crude and which boils in the range above about 500F., it ispreferred to contact the same for a period of from to 25 minutes,preferably from 10 to minutes, at a suitable temperature ranging between370 F. and 700 F., preferably from about 500 F. to 550 F. When treatinga kerosene fraction the time 01 contact should preferably be from 5 to15 minutes at a temperature in the range from 370 F. to 450 F., whereaswaxy constituents should be contacted for a time period from 10 to 20minutes at a temperature'in the range from 7 about 400 F. to 700 F.,preferably at a temperature in therange from about 500 F. to 550 F.Solvent extracts, such as phenol extracts, are treated under conditionswhich depend to a large extent upon the character of the solventextract. Relatively high boiling extracts are contacted for from 5 to 20minutes at a temperature in the range from about 400 F. to 600 F. Whenvery intimate mixing of the oil and alkali are obtainable, improvedresults may be obtained when employing times of contact considerablyless than 5 minutes. The pressure employed should be at least suflicientto maintain the feed oil in the liquid state and in general theoperation is conducted at about atmospheric pressure. However, when oilssuch as naphthas and kerosenes are being treated, pressures as high asabout 10 to 15 atmospheres must be employed due to the high vaporpressure of the oil at the treating temperature.

The quantity of anhydrous fused alkali used per volume of feed materialwill vary considerably depending upon the feed oil being treated and theparticular alkali or alkali mixture employed. Usually the quantity offused alkali utilized will vary in the range from about 0.1 to 3.0volumes of alkali per volume of feed material. In general it ispreferred to employ from 1.0 to 1.5 volumes of anhydrous fused alkaliper volume of feed material. The alkali treated feed material, afterseparation from the alkali in accordance with the preferred modificationof the invention, is then heated and discharged preferably into a vacuumdistillation unit in which temperature and pressure conditions areadjusted to remove substantially the entire quantity overhead.

In order to further illustrate our invention the following examples aregiven which should not be construed as limiting the same in any mannerwhatsoever.

EXAMPLE 1 A crude residuum derived from. a Texas crude was dewaxedutilizing propane as a dewaxing solvent. The slack wax produced had thefollowing inspections:

Melting point, F 118 Expressibleoil and moisturc per cent 11.67 Gravity,A. P. I. 41.5 Initial boiling point, F. (10 mm. Hg) 390 Final boilingpoint, F. (10 mm. Hg) 572 1 As determined by the A. S. T. M. testD30820r.

One volume of this slack wax was then intimately contacted with about0.8 volume of a molten caustic alkali reagent consisting of 92% NaOH and8% NazCOz by weight (fusion point about 510 F.) for about 10 minutes ata temperature of 550 F. The apparatus consisted of a closed vesselprovided with a mechanical stirrer and heated by means of a gas flame.After settling and separating the wax from the reagent thecaustictreated wax was charged to a vacuum still and distilled into a cutequivalent (in volume) to the first of the charge to the fusion pot.The, distillate had the following properties:

Gravity, A. P. I 41.9 Melting point, F 112 Expressible oil and moisture,percent 11.64 Color, Tag-Robinson. 18%

The distillate was subsequentlysweatedto produce a wax with thefollowingcharacteristics:

Melting point, F 122 Color, Saybolt" 28 Colorhold, Saybolt (302? F. for16 hrs. in

presence of copper strip) 17 1 Colorhold test (16 hours at 309 I .}.-60cc. of molten wax isfiltered tlirough filter paper into a test tube. Aclean, dry and polished copper strip one-half inch by two inches isimmersed completely in the wax. and the wax is then heated in a bath at302 F. for 16 hours. end. of this period the wax is filteredthroughpaper and its color determined in a Saybolt colorimeter at 160 F.

r In another operation, similar slack waxwhich .had not been treatedwith fused alkali was vacuum distilled into a similar cut having'thefollowing properties: 7 y Gravity, "A. P. I 41.5

Melting point, F 114 Expressible oil and moisture, percent 14.1 Color,Tag-Robinson 12 This distillate was subsequently treated with fourpounds of sulphuric acid per barrel, and

was then soda neutralized, water washed, dried and sweated. Thefollowing tests were obtained on the swea'ted wax:

Melting point,-F Color, Saybolt o Colorhold, Saybolt (302 F. for '16hrs. in

the presence of copper strip) e -14 EXAMPLE 2 A representative sample ofa paraflin distillate derived from a Panhandle crude was dewaxed in apropane solution to yield a slack wax having the following properties!Gravity, A. P. I. 41.9 Vacuum Engler r r r. (mm.'Hg.)

IBP, F 383 BP, "F 586 This slack wax was treated with; fused caustic asdescribed in Example 1. I The treated wax was redistilled into a 97%overhead cut; the distillate possessed the following characteristics: f

Gravity, A. P. I. 42.3 Melting point, "F 117.5

Color, Tag-Robinson 19% At the p 1 A similar wax which had not beentreated with fused alkali wasvacuum distilled into one cut consisting of97% of the slack wax. The distillate had the following characteristics:

Gravity, A. P. I. 42.5 Melting point, F 113 Color, Tag-Robinson 15 A;

, After acid treatment, soda neutralization, water washing and drying,the wax was sweated to produce a crude scale wax having thefollowingproperties:

Melting point, F 126 Percent scale, based on slack wax 36.2 Color afterpercolation through bone charcoal, Saybolt 28 Colorhold, Saybolt (302 F.for 16 hrs. in

presence of copper strip) 19 {It will be noted from the above data thatthe wax produced from the Panhandle wax distillate by either of the twocaustic fusion methods was distinctly superior withrespect to colorstability to the wax produced by the acid treatment.

EXAMPLE 3 V 0.3 milligram of potassium hydroxide per gram Thisdistillate was then sweated to produce a wax having .the followingcharacteristics:

Colorhold, Saybolt (302 F.) for 16 hrs. in?

presence of copper strip; -14

In anotheroperation'the same distillate from the fused alkali treatedwax was acid treated, soda neutralized, water washed and dried prior tosweating. The sweated wax had the following 9 properties: 7 r 7 Colorafter percolation through bone chariplaced in a sample bottle.

Vis. at 100 F., S. S. U 67 112 269 Vis. at 210 F., S. S. U; 37. 6 43.4Color, Tag-Robinson...; 17% 17 14% Colorhold (16 hrs. at 250 F)Tagobiuson.. .I 10% 12% 9% Neutralization value .01 .007 .02

1 C'olm'hold rest (16 hours at 25 0 F.). cc. of oil is The unstopperedbottle is heated 1:1 an oven at 200 1 for 16 hours. After the sample iscooled to room temperature its color is detcriuined in a Tz1g Robins0ncoloriinetcr.

In another operation (B) a volume of extract secured by phenolextracting approximately 900 Vis./ F. Coastal oil and which had aneutralization value equivalent to 0.1 to 0.3 milligram of potassiumhydroxide per gram of oil was intimately contacted with about 1.5volumes of a molten caustic alkali reagent, consisting of 51% NaOH and49% KOl-I by weight (fusion point about 369 F.) for about 10minutes at atemperature of 550 F. The oil was subsequently treated as in operationA, the finished fractions having the following properties:

Vis. at 10or.,'s-. s. U. 285 '836 1681 3280 5500 948015906 22%; Color,Tag-Robinson. 15 14 12 3 3 l Colorhold (16 hrs. at 'A A 11A 11A 9% 10/49h 250? F.), Tag-Robins0n.. 10% 10%-10% 7% 9% 7% 954 3 coal,v Saybol h I25 Colorhold, Saybolt (302 F. for i16.hrs. in

In a further operation; (C), an extract having a neutralization valueequivalent to 1.3 milligrams of potassium hydroxide per gram of oil,

which was obtained by treating gas oil free total Coastal rerundistillate equivalent to 45% of the crude with 200% of 97% phenol at 180F. with 4% water injection, was treated by (1), conventional rerunningover caustic, and (2) countercurrent aqueous caustic extraction atelevated temperatures followed by rerunning.

The results of these observations were as follows:

OPERATION I Tests on overhead fractions from vacuum distillatz'o'n ophenol extract rerun over caustic Gravity, A. P. I 17. 9 16.1 15.0 13. 712. 2 Vis at 100 F S S U 136 323 V15 at 210 F. S S. U 56.1 76.7 121Color Tag-Robinson... 13 11 9% 8 Colorliold (16 hrs. at 250 Tag-Robinson2% 3 4% 2% 1% Neutralization value 0. 02 0. 05 0.06 0.06 0. 035

OPERATION II Tests on overhead fractions from vacuum distillation ofcaustic extracted phenol extract Gravity A. P. I 17.1 15. 7 14. 3 13.011.6 Vis. at 100 F., S. S. U 201 467 Vis. at 210 F., S. S. U 61.8 87.1128.9 Color, Tag-Robinson 11 9 5 Colorhold (16 hrs. at 250 F.),

Tag-Robinson 2 3% 2% 1% 2 Neutralization value 0.03 0. 05 0.02 0. 050.02

In addition, tests are shown on the following oils obtained by treatingan extract (blend of extract having a neutralization value equivalent to0.08 milligram KOH per gram oil obtained from phenol treating Coastalpale oils of approximately 100, 250, and 900 viscosity at 100 F.) with10 lbs. of 98% H2804 per barrel of oil,.soda neutralizing and distillingin an iron pot still:

Vis. at 100 F., S. S. U 112 388 734 1188 Color, Tag-Robinson 14% 12% 11A 10% Colorhold (l6 hrs. at 250 F.), Tag- Robinson 1. 5 1. 5 1. 0

From these operations it is apparent that extracts produced inaccordance with the methods of aqueous caustic extraction at elevatedtemperatures and. conventional distillation over an excess of caustic,or acid treatment followed by distillation would require additionalchemical and physical treatment to render them color stable, whereasextracts produced in accordance with our method are color stable andrequire no further treatment.

EXAIVLPLE 4 The charge stock employed in this operation comprised areduced cracked naphtha having the following properties:

Gravity, A. P. I 40.2 IBP, F 289 FBP, F 477 Copper No 1.0 Sulfur (lamp),per cent 0.05

was charged to a vacuum still and distilled into an overhead cutamounting to of the charge to the fusion pot. The properties of thisdistillate are tabulated in Table A below.

A second portion of the reduced cracked naphtha was treated with 3pounds of 98% H2804 per barrel of naphtha. After separating and removingthe sludge, the acid treated naphtha was subjected to a water wash, acaustic wash, then another water wash, and (finally) it was distilledinto an overhead cut amounting to 95% of the charge to the acid treater.The properties of this finished distillate are also presented in Table Abelow.

TABLE A Distillate gg from naphtha naphtha treated Wei-nted with Wlthacid fuse? caustic Gravity, A. P. I 42.5 42.8 Distillation:

I. B. P., F 289 286 F. B. P F 400 388 10% off at, E 299 297 50% Off at,F---" 316 312 95% 0 at, F 376 366 Standard heat color 1 (l6 Saybolt +8+20 Direct oxidation color, Saybolt 4 +21 Sunlight stability color,Saybolt:

2-hour exposure +6 +17 4-hour exposure 5 +16+ Octane number, A. S. '168.2 70.1 Sulfur (lamp), percent 0.017 0.015

lStamlard heat color (16 hours at 212 F.).'100 cc. of oil are placed ina bath at 210 F. During the first half hour of the test the stopper isleft off the bottle and during the remaining 15 hours of the test thebottle is kept stoppered. If any evaporation occurs the loss is made upby the addition of naphtha having a 30 color. The color is determinedbefore and after the test by means of a Saybolt colorimeter.

It will be noted that, with respect to color stability and octanenumber, the fused-caustic treated product is superior to the acidtreated product. Attention is also called to the fact that the fusedcaustic treatment effected about the same drop in sulfur content of thenaphtha as did the acid treatment, the latter being considered aparticularly good means of lowering the sulfur content of oils. Thefused alkali treatment produced an oil that was sweet to thedoctor test.This result is secured when treating naphthas boiling in the motor fuelboiling range.

EXAMPLE 5 A high-sulfur kerosene distillate derived from a West Texascrude was employed as the charge stock in this operation. After beingcaustic washed for removal of hydrogen sulfide, this distillate had thefollowing properties:

Gravity, 'A. P. I 43.7 Distillation:

IBP, F 318 FBP, F 547 10% off at, F 367 50% off at, F 423 95% oil at, F531 Color, Saybolt +15 Copper No 33 Silver No 27.0 Sulfur (lamp), percent 0.11

A portion of this kerosene distillate was treated with about 0.8 volumeof molten caustic alkali reagent consisting of 92% NaOH and 8% NaaCOa byweight (fusion point about 510 F.) for about 10 minutes at a temperatureof 550 F. The apparatus consisted of a closed vessel provided with amechanical stirrer and heated by means of a After settling andseparating the kerosene from the reagent, the caustic treated kerosenewas charged to a vacuum still and distilled into a 95% overhead cutbased on the charge tothe fusion pot. The properties of this distillateare tabulated in Table B below.

Another portion of the high-sulfur kerosene distillate was treated with5.0 pounds of 98% H2804 per barrel of oil. After settling and removingthe sludge from the oil, the latter was doctor sweetened and distilledinto a 95% overhead cut based on the charge to the acid treater. Thisdistillate was doctor sweetened again; after which, it was water washedand dried. The properties of the oil thus treated are tabulated in TableB which follows:

TABLE B Distillate fg? from k r kerosene $2123 treatedwith fused withcaustic Gravity, A. P. I 44. 2 43. 9 Distillation:

I. B. P., F 330 327 F. P., 520 517 10% ofl at, F 367 362 50% off. at, F418 413 95% off at, 506 504 Color, Saybolt +27 +27 Direct oxidationcolor, Saybolt -9 +20 Copper No. after redistilling oil, prior to finalsweetenin 0. 1 Silver No 10.0 2. 0 Sulfur (lamp), percent 04 09 Theabove data show that fused caustic treatment of kerosene distillatesproduces an oil superior, as judged by color stability and silvernumber, to similar oils produced by th'econventional method of acidtreating, followed by doctor sweetening, distilling and thenresweetening. It will be noted particularly that the fused caustictreatment followedby distillation substantially sweetened the oil,effecting a reduction in copper number of the oil from 33 to 0.1. Thecopper number is a measure of the amount of mercapta sulfur present inthe oil.

The process of the present invention is not to be limited by any theoryor mode of operation but only by the following claims in which it isdesired to claim all novelty insofar as the prior art permits.

We claim: I

1. A continuous process for the productionof color stable waxesfromcrude slack wax com prising the steps of subjecting the liquid slack waxto intimate mixing with a liquid anhydrous molten caustic alkali at atemperature above the fusion point of said alkali, separating andremoving the liquid treated wax from the alkali, recycling the moltenalkali to' the wax-alkali mixer, reheating and distilling the liquidslack wax into a suitable fraction under mild thermal conditions,sweating the resultant distillate to yield a scale wax of suitable=melting point, and percolating the sweated wax through bone charcoalfor the production of the required color.

2. A continuous process for the production of color stable waxes fromslack wax comprising the step of subjecting liquid slack wax to intimatemixing with a liquid anhydrous molten caustic alkali at a temperatureabove the fusion point of said alkali, separatingand removing the liquidtreated wax from the alkali, recycling the molten alkali to thewax-alkali mixer, reheating and distilling the wax into suitablefractions under mild thermal conditions, acid treating, sodaneutralizing, water washing, drying, and sweating the resultingdistillate to a suitable melting point, and percolating the sweated waxthrough bone charcoal for the production of the required color.

3. A process in accordance with claim 1 in which the anhydrous moltenalkali is a mixture comprising about 20% to 100% caustic soda and aboutto 0% caustic potash.

4. A process in accordance with claim 2 in which the anhydrous moltenalkali is a mixture comprising about 20% to caustic soda and about 80%to 0% caustic potash.

5. A process in accordance with claim 1 in which the anhydrous moltenalkali is a mixture comprising about 75% to 100% caustic soda and about25% to 0% sodium carbonate.

6. A process in accordance with claim 2 in which the anhydrous moltenalkali is a mixture comprising about 75% to 100% caustic soda and about25% to 0% sodium carbonate.

7. A method of treating slack wax to obtain a purified wax comprisingthe steps of intimately contacting molten slack wax with anhydrousmolten alkali at a temperature above the fusion pointof said alkali butno higher than 550 F., subsequently removing the liquid wax from thealkali and vaporizing said wax to obtain a distillate fraction.

8. A method in accordance with claim 7 in which the molten wax iscontacted with a mixture of sodium hydroxide and sodium carbonate forapproximately 10 minutes.

:59. A method of treating slack wax to obtain a purified wax comprisingthe steps of intimately contacting liquid slack wax with anhydrousmolten alkali-at a temperature above the fusion point of said alkali butno greater than 550 F. settling the mixture, separating and removingtreated wax from the alkali and subsequently vacuum distilling said waxto obtain a distillate fraction.

10. A method in accordance with claim 9 in which the method iscontinuous and the alkali removed from the settling step is recycled tothe contacting step.

REUBEN F. PFENNIG. CLAUDE R. DAVIS.

